[References to Popper's concept of 3 worlds occupy a central position in ontological and human ecological questions in the recent literature on theoretical geography. This article shows that Popper's ideas and concepts have not been understood appropriately, which causes problems for integrative research. First, we critically review the discussion of Popper's concept of 3 worlds in geography. We criticize the popular ontological interpretation, and additionally we point out that Popper's evolutionary basis has been consistently neglected. Subsequently, we depict an understanding of Popper's concept of 3 worlds which seems most plausible. We portray his intentions and elaborate on the inevitable evolutionary foundation of the most plausible interpretation of his theory. Finally, perspectives for human ecological research in geography on the basis of theories of evolution and emergence will be outlined].